Vaccination is a procedure whereby an immune response to an antigen can be achieved to protect a host from infection. Some antigens elicit a strong immune response and some a weak response. Attempts have been made to enhance the immune response of weakly-immunogenic materials. The use of chemical adjuvants achieves such potentiation but generally such materials are toxic chemicals which cannot be used in humans.
Another procedure for achieving potentiation is to conjugate the weakly-immunogenic material to a strongly-immunogenic material and administer the conjugate in a vaccine. For example, a conjugate of the capsular polysaccharide of Haemophilus influenzae type b to diphtheria toxoid, as described in U.S. Pat. Nos. 4,496,538 and 4,619,828, or a conjugate of a weak antigen to a monoclonal antibody targeting antigen-presenting cells, as described in U.S. Pat. No. 4,950,480, may be employed.